1. Field of the Invention
This invention relates to vacuum suspension prosthetic sockets.
2. Discussion of Related Art
Amputees have retained prosthetic devices on their residual limbs using various vacuum or suction arrangements for many years, particularly since the advent of soft cushion liners that are worn between the residual limb and the prosthetic socket. Typically, a one-way valve is provided at a distal end of an otherwise closed socket arranged to receive the distal end portion of a residual limb whereby air in front of the distal end of the residual limb may be exhausted until the residual limb and its donned liner are fully inserted into the socket.
The one-way valve thereafter is maintained in a closed condition and forces tending to separate the prosthetic socket from the residual limb are resisted by induced sub-atmospheric pressure between the distal end of the residual limb and the distal end of the socket.
It is necessary, of course, with vacuum suspensions to maintain the sub-atmospheric pressure or vacuum at the distal end of the socket and appropriate sealing sleeves and other arrangements are typically provided to prevent influx of air around the distal end of the residual limb and into the distal end of the socket. Obviously, with a vacuum suspension system, any significant loss of vacuum will result in separation of the prosthetic socket from the residual limb unless an additional element is provided to retain the socket attached to the residual limb.
It has been recognized in the prior art to provide a vacuum reservoir chamber maintained at sub-atmospheric pressure and in communication with a prosthetic socket for the purpose of maintaining an appropriate partial vacuum within the socket to compensate for variations in volume of the residual limb while the prosthetic socket is worn and to compensate for air leakage around the residual limb. U.S. published patent application No. U.S. 2001/0005798 A1 published Jun. 28, 2001 discloses a reservoir maintained at sub-atmospheric pressure mounted on a pylon of a prosthetic device and communicating with the interior of the prosthetic socket via a conduit connected to the reservoir. Such arrangements are unwieldy and tend to add to the weight of the prosthetic device suspended from the prosthetic socket. The added weight contributes to added inertia which would be noticeable to a leg amputee.
U.S. Pat. No. 2,530,285 issued Nov. 14, 1950 describes a chamber in the distal end area of a prosthetic socket that may be maintained at sub-atmospheric pressure, such chamber being integrated with the prosthetic socket, but having a movable diaphragm as a side wall of the chamber for the purpose of actuating a knee lock of a prosthetic device carried by the socket. This patent also shows the distal end of the residual limb extending into the chamber, so that the total effect of the diaphragm and the residual limb extending into the chamber is to produce a variable volume chamber as the diaphragm and the residual limb move during implementation of the prosthetic socket. The pressurization of the vacuum chamber in accordance with this patent is necessary to produce motion of the diaphragm to effect locking of the knee joint carried by the prosthetic socket. Movement of the prosthetic socket disclosed by this patent tending to separate the socket from the residual limb would result in deformation of the diaphragm in a reverse direction into the chamber thereby creating insecurity on the part of the amputee as to whether or not an appropriate vacuum was being maintained below the residual limb.
U.S. Pat. No. 2,671,225 describes a prosthetic socket having a flexible inner sac of soft, elastomeric resin permanently bonded to the interior of a hard outer, load bearing socket wherein a chamber at the end of the sac is provided between the distal end of a residual limb inserted into the sac and the distal wall of the sac, such chamber being in communication with a one-way valve that permits exhaust of air between the residual limb and the distal wall of the sac but does not permit air to enter the chamber. This form of suspension liner suffers from the problem that the sac itself is flexible and even though there is a vacuum maintained at the distal end of the sac, the sac itself can move relative to the outer socket due to its flexible characteristics. Thus, the chamber is not actually a reservoir, but merely a chamber from which air has been exhausted and into which the admittance of air is prevented in an attempt to create a vacuum suspension system.
U.S. Pat. No. 2,533,404 discloses a one-way exhaust valve at the distal end of a prosthetic socket for exhausting air between the distal end of a residual limb inserted into the socket and the disclosed distal wall of the socket. While the volume of the chamber at the distal end of the prosthetic socket is relatively fixed, nevertheless, there is no reservoir provided to compensate for any leakage of air into the chamber or to compensate for the varying volume of the residual limb within the prosthetic socket.
U.S. Pat. Nos. 5,702,489 and 6,287,345 granted respectively on Dec. 30, 1997 and Sep. 11, 2001 describe other approaches to vacuum suspension systems whereby a relatively pliable end wall element is inserted into the distal end of a rigid, load-bearing prosthetic socket and the end wall is provided with an air chamber integrated therein in communication with a valve arrangement and a quick-disconnect port via which gas may be sucked from the socket by means of apertures provided in the flexible cushion end wall. Obviously, in accordance with this construction, the distal end of a prosthetic limb bearing against the flexible end wall would have an effect on the volume of the chamber within the end wall within which a sub-atmospheric pressure has been established.
U.S. Pat. No. 6,231,616 issued May 15, 2001 describes a prosthetic socket including an arrangement for establishing a vacuum between a liner donned on a residual limb and the inner surface of a prosthetic socket.
German Patent No. 745981 issued on May 22, 1944 describes a suction suspension system for a prosthetic socket wherein leg motion of a prosthetic device actuates a suction pump that creates a vacuum between the distal end of a residual limb and the distal end wall of an outer socket.
U.S. Pat. No. 5,658,353 discloses another arrangement whereby a suction pump it utilized to create suction between the distal end of a residual limb and the inner wall of a socket arranged to receive the residual limb to facilitate insertion of the limb and to the socket.
Thus, it is evident that the use of suction to facilitate insertion of a residual limb into a load-bearing socket and the use of suction to maintain the residual limb within the socket is well-known in the prior art. What is obviously lacking in the prior art is a suitable arrangement for maintaining a sub-atmospheric pressure between the residual limb and the inner walls of a socket despite variations in volume of the residual limb and further despite minor air leakage around the residual limb tending to relieve the vacuum within the socket.
Ideally, a reservoir containing a volume of sub-atmospheric pressure integrated with a load-bearing socket would provide insurance against volume variations of a residual limb and minor air leakage into the socket. Such an arrangement furthermore would need to be light weight and smoothly integrated with a prosthetic socket so as not to unduly enlarge the outer profile of the socket. It would be highly desirable to provide a load-bearing prosthetic socket that may be readily coupled to a prosthetic device in a conventional manner while providing a vacuum reservoir chamber within the socket itself and without diminishing the strength and load bearing characteristics of the socket. It also would be highly desirable to provide such a vacuum chamber with rigid walls capable of maintaining a constant volume during implementation of the prosthetic socket containing the reservoir vacuum chamber.